Short answerCompare the IPv4 in the WAN section of the router with the address that the site sees. Private WAN or 100.64.0.0/10 indicates additional translation, but not every NAT is located at the ISP.

When does it make sense to check the address?

You have configured port forwarding for your server or camera, but you cannot connect from outside. One possible explanation is that there is another address translation node in front of the home router. But a firewall, an incorrect port, and the absence of a running service give a similar result.

First, find out the address that the site sees. Then open your router settings and find WAN IPv4 under Internet, Connection or Status. Do not use the control panel address from the address bar: this is usually the address of the router within your home network.

CGNAT and public IP check

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How to read the comparison result

WAN IPv4 What can be concluded
10.x.x.x, 172.16–31.x.x or 192.168.x.x Private addressing is used in front of the router; another home router or NAT provider is possible
100.64.x.x–100.127.x.x An address from a special general addressing range; strong CGNAT trait
The public address matches the visible one on the site No CGNAT detected in this session
Public addresses vary Check VPN, proxy and route; comparison alone is not enough

A special range for general addressing is defined in RFC 6598. It is different from the normal home private ranges. None of these results by themselves tell you who owns the equipment in front of you.

Why doesn't match open ports

Public IPv4 does not guarantee the availability of an incoming connection. You need a working service, a suitable forwarding rule, firewall resolution and no restrictions from the provider. This test does not scan ports or check all of the conditions listed.

Also, don't confuse "public" and "static". The address may be accessible from the Internet, but change after reconnection. You should find out the conditions for allocating an address from your provider.

What prevents comparison

VPNs and proxies can change the address visible to the site. The browser can access the site over IPv6 while you are viewing the WAN IPv4. In this case, comparing different families does not make sense, and the service should not declare the result “gray IP”.

When running Calcomera locally, the server sees the local connection. It also does not allow you to find out the public WAN. For a home setup with a modem and a separate router, check to see if both devices are in routing mode.

What to ask your provider

Describe your task - incoming connection to your own service - and clarify whether public IPv4 is provided, whether it changes and whether the necessary ports are limited. Don't order a static address just because of the word "gray": you may need a different service or a change in your home network design.

Sources and methodology

Calcomera editorial teamTests, explanations and open limitations of the method. About the editors